Typically, sound is produced by driving a current through wires to a speaker that outputs the current as sound. The current causes the speaker driver to vibrate or move resulting in the creation of the sound. The motion of the speaker driver produces sound pressure that may travel out of the speaker enclosure and ultimately is received at an ear of the listener.
In some cases, the sound pressure created by the speaker travels into the ear upon which the audio device is worn. In some situations, the sound pressure may be reflected back towards the speaker by the eardrum. Some portion of the sound pressure is captured by the speaker driver acting as a microphone creating current that is fed back into an amplifier of the sound system generating the audio signal being output by the audio device. This current, termed, ghost current will mix destructively with the current being generated by the amplifier based on the desired audio signal and degrade the quality of the audio being output by the audio device.